the query runs after the loading process has begun; this is so that the subqueryload takes precedence over other loaders that may be hitting the same attribute due to other eager/noload situations at the wrong time. [ticket:2887]
This enables the subquery eager loader strategy to apply a DISTINCT to the innermost SELECT subquery, to assist in the case where duplicate rows are generated by the innermost query which corresponds to this relationship (there's not yet a general solution to the issue of dupe rows within subquery eager loading, however, when joins outside of the innermost subquery produce dupes). When the flag is set to ``True``, the DISTINCT is rendered unconditionally, and when it is set to ``None``, DISTINCT is rendered if the innermost relationship targets columns that do not comprise a full primary key. The option defaults to False in 0.8 (e.g. off by default in all cases), None in 0.9 (e.g. automatic by default). Thanks to Alexander Koval for help with this. [ticket:2836] Conflicts: lib/sqlalchemy/orm/relationships.py
``query(SubClass).options(subqueryload(Baseclass.attrname))``, where ``SubClass`` is a joined inh of ``BaseClass``, would fail to apply the ``JOIN`` inside the subquery on the attribute load, producing a cartesian product. The populated results still tended to be correct as additional rows are just ignored, so this issue may be present as a performance degradation in applications that are otherwise working correctly. [ticket:2699]
- paths now store Mapper + MapperProperty now instead of string key, so that the parent mapper for the property is known, supports same-named properties on multiple subclasses - the Mapper within the path is now always relevant to the property to the right of it. PathRegistry does the translation now, instead of having all the outside users of PathRegistry worry about it, to produce a path that is much more consistent. Paths are now consistent with mappings in all cases. Special logic to get at "with_polymorphic" structures and such added also. - AliasedClass now has two modes, "use_mapper_path" and regular; "use_mapper_path" is for all those situations where we put an AliasedClass in for a plain class internally, and want it to "path" with the plain mapper. - The AliasedInsp is now the first class "entity" for an AliasedClass, and is passed around internally and used as attr._parententity and such. it is the AliasedClass analogue for Mapper.
subclasses are being loaded using with_polymorphic(), each subclass contains a relationship attribute of the same name, and eager loading is being applied to one or both. This is an ongoing bug which can't be immediately fixed, so since the results are usually wrong in any case it raises an exception for now. 0.7 has the same issue, so an exception raise here probably means the code was returning the wrong data in 0.7. [ticket:2614]
become an externally usable package but still remains within the main sqlalchemy parent package. in this system, we use kind of an ugly hack to get the noseplugin imported outside of the "sqlalchemy" package, while still making it available within sqlalchemy for usage by third party libraries.